Current state of the art cellular phone technologies have a difficult time operating in a mobile environment where one of the phones is located in a moving car. As the car moves between buildings or under bridges, the communication often breaks up or has periods of extreme noise. In part, the difficulty in maintaining clear communications results from the fact that the characteristics of the communication channel between the cellular phone and the receiving station change very rapidly as, for example, when the car passes under a bridge. In general, although numerous attempts have been made to accommodate mobile transceivers, current radio transceivers deal with highly dynamic channel conditions relatively poorly.
In current wireless communications systems, a major source of channel degradation is Inter-symbol Interference (ISI). Conventionally, many different types of equalizers are utilized to try to prevent ISI. One group of equalizers are based on the Viterbi Algorithm (VA). VA approaches utilize a method to estimate the channel impulse response. Per-Survivor Processing (PSP) is a new technique to apply channel estimation to all the survivor paths. Although this approach has improved the overall system performance in uncertain environments, it still does not satisfactorily eliminate the dependency between different paths and thus can still be problematic where the channel characteristics change very rapidly.